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Flashcards in dentin Deck (39):
1

dentin does not have

b.v, whole cells

2

dentin has

odontoblast process and nerve endings

3

dentin has a greater ____ than enamel

compressive strength

4

dentin cushions...

overlying enamel. so conditions that affect dentin also affect enamel (DI)

5

dentin takes what configuration at the DEJ?

scalloped...this facilitates adhesions

6

what stage of odontogenesis does dentinogenesis occur

bell stage

7

what happens in the late bell stage

1. inner epithelial cells differentiate into ameloblasts
2. mesenchymal dental papilla cells differentiate into odontoblasts
3. dentin secreted
4. enamel secreted

8

in what direction does dentinogenesis go

cusp tips to cervix and from periphery to pulp center

9

what induces odontoblast differentiation

signal secreted from enamel organ/enamel knot (signaling or growth factors)

10

what is one molecule though to play a part in odontoblast differentiation

Wnt10a. 1st expressed in the enamel knot, then in pre-odontoblasts at the cusp tip and then cervical. Expression immediately precedes the wave of odontoblast differentiation

11

supporting evidence that Wnt10a induces...

Dentin sialophosphoprotein (secreted by mature odontoblasts)

12

what is the unmineralized organic matrix of dentin called

predentin

13

requirements for mineralization of dentin

1. Ca and Phosphate
2. initiation of crystal formation (by 2 mechanisms)

14

where does the phosphate for dentin mineralization come from

plasma and cleavage of organic molecules containing phosphate in odontoblasts by alkaline phosphatase

15

2 stages of dentin formation

1. mantle
2. circumpulpal

16

mantle dentin formation

principle component of matrix= collagen type 1 (large fibrils)
secreted from odontoblasts
procollagen secreted is oriented at right angles to DEJ
matrix vesicles (Ca and PO crystals)

17

circumpulpal dentin formation

smaller type I collagen fibrils, parallel to basal lamina/DEJ
proteins synthesized and secreted from odontoblast (with Ca and P ions) processes that bind to collagen and precipitate it out to form crystals

18

differences b/w mantle and circumpulpal dentin

mantle dentin more organic, mantle dentin less mineralized, so DEJ more vulnerable to caries

19

dentin phosphoprotein

highly phosphorylated, high in serine/aspartic acid, acidic and anionic, long chain of polar a.a...hypothesis is that it precipitates Ca ions from tissue fluid which initiates mineralization. gene is DSPP which is cleaved into DPP

20

mineral phase of dentin

hydroxyapetite with 4-5% carbonate...crystal size is smaller than enamel with random orientation

21

organic phase of dentin

processes of cells, extracellular matrix

22

extracellular matrix of dentin has

collagen type I (90%) and non-collagenous proteins (non specific, mineralized tissue specific, dentin dominant)

23

dentinogenesis imperfecta

dentin forms improperly...mutations in DSPP. dominant negative mutation (mutated DSPP traps normal protein)

24

mutations in DSPP

1. changes in 1st 3 a.a are critical for moving DSPP though the RER (stuck in RER)
2. base pair deletions causing a frameshift in polar a.a region...changes it from polar to uncharged (stuck at cell membrane)

25

contents of dentinal tubule

fluid, nerve fibers, odontoblastic processes

26

dentinal tubules are

@ right angles to the DEJ, s-shaped at the crown, straighter in the root, more branching at the DEJ than the DCJ

27

# of dentinal tubules in greater...

in inner dentin compared to outer

28

the diameter of tubules is greater...

in inner dentin. tubules occupy less room at the DEJ that DPJ. permeability and wetness increase towards the P-D border

29

primary dentin

formed until completion of root development, most dentin, mantle and circumpulpal dentin (more mineralized)

30

secondary dentin

formed after root development, slower rate, throughout life, along entire circumference of the pulp chamber (heaviest on the roof and floor)

31

tertiary/reparative dentin

produced in specific location in response to noxious stimuli, irregular, under caries

32

intertubular dentin

b/w tubules, large volume, less mineralized

33

intratubular/peritubular dentin

lining tubules, smaller volume, greater mineralization, ring is wider near DEJ

34

translucent/sclerotic dentin

tubules completely filled with intra/peritubular dentin...translucent (process of aging) and sclerotic (accelerated deposition due to caries/attrition). increases with age

35

dead tracts

tubules dried out and filled with air

36

intraglobular dentin

hypomineralized dentin just below mantle dentin

37

individual foci of calcification that fuse are called

calcospherites...if they don't fuse= interglobular dentin

38

tome's granular layer

hypomineralized dentin at the periphery of the dentin near the CEJ

39

growth lines of dentin are called

lines of von ebner ...exaggerated due to tetracycline